For more than a decade, there has been considerable effort devoted to the producing of synthetic thermoplastic sheet material having differentially colored bands or layers therein. The materials originally developed employing differentially colored bands are of the type illustrated in U.S. Pat. No. 2,985,558 granted May 23, 1961 to William P. Rowland and it can be seen that the bands of the differentially colored material extended in a direction generally parallel to the direction of extrusion. Other techniques for introducing differentially colored material in the body of the extruded sheet are shown in U.S. Pat. No. 2,632,204 to Murray and U.S. Pat. No. 2,803,041 to Hill et al.
For some applications, it is extremely desirable that the differentially colored materials not extend in a parallel pattern to the direction of the extrusion and this is particularly so in the optical frame industry wherein patterns of varying appearance are constantly desired. Various techniques have been proposed to provide interruption in an otherwise parallel pattern for the differentially colored material, among which is that illustrated in U.S. Pat. No. 3,274,646 to Krystof. Techniques for producing unusual multilayered and swirl patterns are described in U.S. Pat. No. 3,443,278 and U.S. Pat. No. 3,531,828 to Jan P. Nauta and U.S. Pat. No. 3,422,175 to William P. Rowland.
One of the most popular patterns over the past years has been a Havana pattern which effectively comprises a basketweave design wherein differentially colored material from a crosshead extruder is discharged from two series of vertically spaced ports fed intermittently by means of screws or the like. Such designs have proven quite popular and there have been patterns produced using two different colors for the bands providing the basketweave design.
One of the objections to the Havana pattern has been that all of the components of color extend diagonally of the sheet material. There have been efforts to superimpose color effects which would soften the basketweave design which have frequently included laminating techniques.
It is an object of the present invention to provide a novel and highly attractive synthetic plastic sheet material having a multiplicity of bands of differentially colored resin disposed within a matrix resin and in which the bands have striations extending longitudinally of the sheet material.
Other objects and advantages of the invention will appear from the following description.